I have noticed that there is a lot of information about the older carburetor Vespa engines on the web but hardly anything about our modern injected Vespa engines. Because a lot is controlled from the ECU it's often vague when dealing with injected engine complaints.
After a lot of googling I found out that there is a lot of information for the other injected Italian bikes (Ducati and MotoGuzzi) but hardly anything for our injected Piaggio's. Their information is very useful so I have combined it in this Vespa tutorial.

There are actually 2 programs (freeware/donation) that should work with the Magneti Marelli MIU ECU placed in our injection Vespa's.

To start with the pc/laptop. I run IAWdiag on an old Windows XP laptop from 2004 and a Windows 7 starter Netbook from 2009, so the specifications are very low and the older pc/laptop will do the job.

About the cables: To start with the VAG KKL cable, I have bought two of them and only one is working fine. Both bought on eBay but they sell them on Amazon as well.
The first, not working one, has a cheap Chinese CH340 chipset. The other cable has an original FTDI chipset and is working great.
You can find this item on eBay (item 161743974836)

The second cable is a Fiat OBD cable with 2 crocodile clamps (red + and black -).
You can find this item on eBay

IMPORTANT: check the correct wiring of the Fiat OBD cable. It should be wired according the scheme below. If this is not the case you can damage your ECU.

When you have all the items mentioned above you can start the installation.
Install the FTDI drivers before connecting the VAG KKL cable.
Don't use the drivers from the disc that comes with the cable.
Download the drivers from the FTDI site (http://www.ftdichip.com/Drivers/VCP.htm).

Connect the crocodile clamps to the battery (connect red clamp first, then black).

IMPORTANT: do not connect the diagnose plug/connector.

Start the AdapterTest program, fill in the COM port and press "connect".

When test 1 and 2 are successful press "disconnect".

If the tests are not successful, then there is something wrong with one of the cables. Do not connect the cable to the ECU to prevent any damage. Check again the scheme of the Fiat OBD and open the VAG KKL cable to see if there is not a fake FTDI chip installed (like my first Chinese cable).

If the tests are ok, both VAG KKL and Fiat OBD are ok, and you can connect the diagnose plug/connector.

You can now start IAWdiag, fill in the language, COM port and ECU type.

Go to the upper left en press "file" - "connect" and follow the instructions on your screen.
When the ECU is properly connected you can find the data of your ECU on the bottom left of your screen. You can now select the parameters you want to monitor, read out the fault messages or do some static tests.
You can also start your engine to read out more parameters.

IMPORTANT: Don't do a TPS reset. These ECU's are pre calibrated at the factory.

When you want to quit and your engine is running, use the "kill switch" to turn off the engine.
Then go to the upper left en press "file" - "disconnect" and follow the instructions on your screen.

So far the information how to make your own diagnose tool. I hope that this tutorial is useful to many modern (injected) Vespa riders and enjoy your own DIY diagnostic tool.

Extra information: The IAWdiag software designer has made another program called IAWMIU3GReader, IAWMIU3GWriter and IAWMIU3GEEPROMTool. With these programs you can read and write to your MIU ECU so it should be possible to adjust your mapping.
They can downloaded from: http://www.von-der-salierburg.de/download/GuzziDiag/

JPDiag (http://jpdiag.akress.com) is also working with the ECU's listed above.
Tested with the same cables and windows drivers from the tutorial above.
IMPORTANT: test the Fiat OBD and VAG KKL FTDI cable by following the tutorial above to prevent damage to your ECU.

Install JPDiag and follow the installation instructions.

Connect the USB cable to the pc/laptop
Connect the clamps to the battery (connect red clamp first, then black)
Connect the diagnose plug/connector.

Start JPDiag and select your preffered language.

Select the correct cable. If you use the FTDI cable from the tutorial above, select Galletto Cable and press "ok"

Press the lower radio button on the right side of the "connect" and press "connect"

The ECU is now connected and you can see the ECU information.

To get a free license press the blue "copy" button.
This button will automatically open your browser and connects to the JPDiag webpage (http://jpdiag.akress.com/jpdiag.php), fill in the scooter type and email address and you'll receive a license file by mail.
Copy cle.lic file without renaming it into JPDiag directory, usually it's located in c:\program_files\jpdiag\

Restart JPDiag and you can use now all the features.

If you want some more information about the Magneti Marelli MIU G3 ECU you can check the .pdf document below.
The document is written for both single as twin cylinder bikes (MotoGuzzi V7) but the MIU ECU basics are the same for both so you can use it as reference.

Last edited by Pilaf on Sat Feb 10, 2018 1:19 am; edited 9 times in total

Great Tutoraial! I just installed the programm and read my MIU1 GTS300 - all working fine. I´m just wondering how I could read/write this type of ECU. I found the MIU3G reader & writer but unfortunately not the programm for my old MIU1.

When you are you using JPdiag sent JP a mail and ask him about the price (payware) for a single reader/writer licence for the MIU1 version.

About the mapping, i'm still in the expirimental phase and learning how and the meaning of all the parameters in the mapping. No experience on the MIU1, only MIU3. What I'm most interested in is the difference between the Euro3 and Euro4 mapping. I downloaded both mappings (2015 & 2017 GTS300) and as far as I can see the mapping of the Euro4 is overall "leaner" so that explains the little loss in horsepower.

great info on DIY tests. ran all tests with no error codes. at 60 mph on a flat bike surges real bad.full throttle good. no throttle good , letting off alittle or tryin to stay around 60 to 65 real shaky. only 5k on it. went thru belt & clutch all good. dirty injector? any ideas or help appreciated

great info on DIY tests. ran all tests with no error codes. at 60 mph on a flat bike surges real bad.full throttle good. no throttle good , letting off alittle or tryin to stay around 60 to 65 real shaky. only 5k on it. went thru belt & clutch all good. dirty injector? any ideas or help appreciated

First of all, is your 2015 GTS still under warranty? If so, let the dealer solve your issue.
If not, check the software version. My GTS just received an 2017 update (because i had cutout problems) and i compared the old and new mapping. They have changed the fuel map and the timing map.
If your GTS is uptodate, no fault codes in the ecu and there are still problems then it's better to post your problem on the modern vespa general forum and ask for help, more viewers and more tips.

I recently had nu mapping installed. no change. dealer says try f.i.cleaner
so I ordered malossi lambda emulator. will post results.will post on general
still nu to forum and where to find things Thanks

by the way my vespa is stalling when iddle and the engine check light is on
when the engine dies i have to twist on the grip while pushing start buttom and when parked it drops a little bit of gasoline
besides that it is running very nice with no problens
i made a mistake and tryied to ajust the iddle screw my bad
so now i will try to find if the injector is bad first, the vespa is 2006 but only with 800km, maybee old gasoline did something

Sorry to hear that you've adjusted the ECU screw. There is a possibility to put it back in the default but you need the .bin file.
Import the file in TunerPro as mentioned above. The default TPS is in the left corner, for my MIU3G is 3.8 degrees.
When you start one of the diagnose tools you can see the actual TPS degrees.
Now you can try to adjust the screw so that the actual TPS matches the default TPS from the .bin file.
It is a though job and takes some time to get is right but i did it before with a messed up ECU and it worked well.

From your fault codes list there are multiple items which can cause the engine light.
Are the fault codes resetable or not? If so reset them. Start the engine with diagnose tool connected with the fault page active. See if there is a fault popup and try to find out which one pops up first.
The P0130 (lambda sensor) is one of them and the easiest to replace. Could be that the probe is broken and sends a rich signal to the ECU causing a fuel overflow.
Try to replace that one and if the new probe is not solving the problem you can troubleshoot further and try the main MV forum, there is a lot of knowledge available.

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